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Develop Replacement Heifers

Posted Dec. 1, 1996

One of the most difficult aspects of cow-calf production is getting yearling heifers properly developed to breed at one year of age. This is particularly difficult in spring-calving herds where heifers must grow and develop during the dormant season. By now, most managers of spring-calving herds have selected their replacements. Ideally, about 50% more heifers should have been selected at weaning time than will be needed as replacements.

The additional heifers are kept for two reasons. First, this allows additional selection before breeding. There are always a few heifers that do not develop adequately. Second, conception rates in limited breeding seasons are rarely 100%. To compensate, plan to breed 15-25% more heifers than are needed as replacements.

Another thing that should be considered at the time of initial selection is age. Age is a major factor affecting puberty in beef heifers. Beef heifers usually reach puberty between 10 and 15 months of age (if properly developed). Do not waste time and money developing heifers that will not be old enough to breed.

Once heifers are selected at weaning time, producers should carefully plan their development programs. If a stepwise procedure is used to plan and implement heifer development, many problems can be avoided.

Step 1: Establish Target Weight and Rate of Gain. Yearling heifers should be bred about 30 days before the main cow herd. This gives them more time to recover from the stress of calving so they can re-breed with the main cow herd. Plan your breeding time accordingly. Heifers should weigh at least 65% of their mature weight at the onset of breeding. The following example outlines the process of establishing performance goals.

  • Estimated Mature Weight of Cow Herd: 1200 pounds
  • Average Weaning Weight of Selected Heifers: 550 pounds
  • Weaning Date : November 1 Breeding Date: April 1
  • Calculate Target Weight: 1200 pounds x .65 = 780 pounds
  • Days to Reach Target: 150
  • Required Average Daily Gain: (780 - 550) / 150 = 1.53 pounds per day>/li>


Step 2: Plan Feeding Program. There are two strategies that can be used to achieve desired breeding weight. The first (and most common) is to try to maintain a relatively constant rate of gain. In the example above, target rate of gain would be 1.53 pounds per day. A diet capable of producing this rate of gain must contain approximately 10% crude protein and 60% TDN. Total daily feed intake must be 15-17 pounds of dry matter per head per day during the entire period. This type of diet could come from free choice high quality hay, hay and supplement, small grains pasture or other sources.

A second strategy allows producers to let heifers grow fairly slowly during winter followed by a more rapid growth phase in the early spring. This "slow-fast" method is often cheaper than constant weight gain because less body weight is maintained during the first 2-3 months. However, you must be able to achieve higher rates of gain during the last 60 days. With this method, gains of about .5 pounds per day can be tolerated for the first 60-90 days.

This rate of gain can be attained by feeding about 2 pounds of cottonseed cake per day with free choice native hay or comparable feeds. During the last 60 days, heifers must gain 2.5-3 pounds per day to compensate for the slow gain period. During this period, a high quality diet must be available in adequate amounts. About 18 pounds of dry matter containing 11% crude protein and 65% TDN will be required daily to produce needed gains. Research results indicate no differences in subsequent performance of heifers developed on constant or "slow-fast" regimes.

Step 3: Monitor Heifers During Development. Too often producers fail to realize that performance of heifers is inadequate until it is too late. Regardless of which development program you use, observe heifers carefully. If possible, take periodic weights on at least a few heifers to monitor performance. Adjust feeding accordingly.